Boxing is absolutely a striking sport. Punching, by definition is striking your opponent.
Are there other disciplines that may be more effective when training for a MMA fight, yes. But there is no question that boxing is a striking sport.
Below you state that BJJ is a better striking sport. Whaaaaaat? BJJ is a submission grappling discipline. BJJ is NOT about striking at its heart.
In fact here is a link to striking sports on Wikipedia:
Wikipedia"Combat Sports" redirects here, for The Vaccines' album, see Combat Sports (album).A combat sport, or fighting sport, is a competitive contact sport that usually involves one-on-one combat. In many combat sports, a contestant wins by scoring more points than the opponent or by disabling the opponent. Common combat sports include mixed martial arts, boxing, wrestling, fencing, savate, kickboxing, Muay Thai, Sanda, Tae Kwon Do, Capoeira, Brazilian Jiu-jitsu, HMB, Sambo, Kyokushin, and Kūdō, sometimes even Ninjutsu.
https://en.wikipedia.org/wiki/Combat_sport#Striking_sports[https://en.m.wikipedia.org/wiki/Combat_sport#Striking_sports]
Click on “List of Combat Sports” and that might help you sort things out.